Multiple small nodules in the lower lobes of both lungs generally suggest chronic infection in both lungs and do not exclude metastatic lung cancer, and the diagnosis is usually further clarified by high-resolution CT of the chest. For multiple small nodules in the lower lobe of both lungs, the nodules need to be understood according to the size and nature of the nodules, which mainly include ground glass nodules, partially solid nodules and solid nodules, with ground glass nodules mostly suggesting chronic inflammatory infections. If the nodule is less than 5 mm, no special treatment is usually needed. If the nodule is larger than 8mm, with lobulated, short burr, pleural traction sign, pleural depression sign, etc., further enhanced CT of the chest and percutaneous lung aspiration for histocytology are needed to further clarify whether the nodule has developed early cancer. If there are tumors in other areas, including thyroid cancer, breast cancer, nasopharyngeal cancer, liver cancer, rectal cancer, gynecological tumors, etc., and multiple small nodules appear in both lungs, especially round-like nodules, it is necessary to be highly alert to the possibility of metastatic lung cancer in both lungs, and enhanced chest CT and PET-CT examination should be given if necessary.